Air quality in the national capital will deteriorate to "severe" levels this week when firecrackers will be set off to celebrate Diwali leaving many at risk of respiratory problems, a government scientist said.
The warning, based for the first time on the country's newly launched national Air Quality Index, is significant as the national capital dismissed a World Health Organization (WHO) study in May, which found the capital to have the world's worst air pollution.
The study, which covered 1,600 cities, also said that of the 20 cities with the worst air quality worldwide, the country has 13 of them.
"Delhiites are going to breathe very poor-to-severe air at least for two days," said Gufran Beig, chief scientist at the Indian Institute of Tropical Meteorology, referring to Thursday, when the nation celebrates Diwali, and a day after.
The city of over 16 million people will see its air pollution index jump to 450 from 220 currently. A reading above 401 could put the healthy at risk for respiratory problems and seriously affect those already ill, the new index explains.
Pollution levels in cities have often been compared to Chinese counterparts such as Beijing, notorious for the smog that prompted some Anglophone residents to dub it "Greyjing".
"Over the next three days the air quality will be worse than Beijing because of firecrackers," Beig said, adding that the capital city normally has better air quality than the Chinese capital.
However, a delay in the onset of the winter season will result in lower pollution levels in 2014 as warmer temperature helps pollutants disperse faster, Beig said.
Government officials have appealed to the public to refrain from bursting firecrackers, with the health minister calling for a "silent Diwali" in the national capital to control sound levels.